EP2403112A1 - Barre de stator - Google Patents

Barre de stator Download PDF

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Publication number
EP2403112A1
EP2403112A1 EP10168358A EP10168358A EP2403112A1 EP 2403112 A1 EP2403112 A1 EP 2403112A1 EP 10168358 A EP10168358 A EP 10168358A EP 10168358 A EP10168358 A EP 10168358A EP 2403112 A1 EP2403112 A1 EP 2403112A1
Authority
EP
European Patent Office
Prior art keywords
insulation
stator bar
conductive element
layer
thermal conductivity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10168358A
Other languages
German (de)
English (en)
Inventor
Thomas Baumann
Werner Rumpf
Thomas Hillmer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Technology GmbH
Original Assignee
Alstom Technology AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alstom Technology AG filed Critical Alstom Technology AG
Priority to EP10168358A priority Critical patent/EP2403112A1/fr
Publication of EP2403112A1 publication Critical patent/EP2403112A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/30—Windings characterised by the insulating material
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/32—Windings characterised by the shape, form or construction of the insulation
    • H02K3/40—Windings characterised by the shape, form or construction of the insulation for high voltage, e.g. affording protection against corona discharges

Definitions

  • the present invention relates to a stator bar.
  • the invention refers to a stator bar of a rotating electric machinery such as generators, in particular indirectly cooled generators with more than 100 MW output power and nominal voltage greater 10 kVAC.
  • Stator bars are known to comprise a conductive element made of a plurality of interwoven strands (green bar or plain Roebel bar) with a main insulation around it.
  • main insulation is electric insulation and heat transfer.
  • the typical design of a main insulation focuses on the electric aspects and insulation is designed to withstand high electric fields.
  • the highest electric field occurs at the corners of the conductive element (i.e. at a position within the insulation, but close to the conductive element).
  • the main insulation has to be designed to cope with such high fields at the corners, although for the rest of the insulation such high dielectric strength may not be needed.
  • Heat transfer from the conductor to the stator iron core is also an important function of the insulation, in particular in air-cooled machines. Heat is generated by losses of the high current density and it is removed by transport through the main insulation to the stator iron core.
  • the main insulation is typically made of a mica tape wrapped around the conductive element and impregnated with a resin.
  • DE 198 11 370 discloses to vary the insulation permittivity in the radial direction.
  • Typical values for the dielectric strength of the main insulation are between 2.5-3.5 kV/mm and, for the thermal conductivity (lambda) between 0.25-0.33 W/mK.
  • the heat transfer properties through the insulation should be increased, to let the insulation dissipate the heat generated in the conductive element during operation, without decreasing the insulation electric properties.
  • the technical aim of the present invention is to provide a stator bar whose insulation has improved heat transfer properties when compared to traditional stator bars.
  • the basis of this invention is the finding that most of the breakdowns occurring under high voltage stress occur at the corners.
  • the electric field in the area close to the conductive element is enhanced compared to the field at the flat sides.
  • the electric field enhancement is restricted to a first zone closest to the conductive element having a thickness about one third of the total thickness of the insulation.
  • the electric field E at the corners is even lower than at the flat sides.
  • the stator bar 1 comprises an interwoven conductive element 2 (green bar or Roebel bar) made of interwoven conductive strands 3 having a main insulation 4 around it ( figures 1 and 2 ).
  • the main insulation 4 comprises at least two layers 5, 6 wrapped one onto the other.
  • an inner layer 5 has a dielectric strength of at least 3 KV/mm and the outer layer 6 has a thermal conductivity of at least 0.5 W/mK, preferably 1.0 and more preferably about 1.5 W/mK.
  • the thickness t of the inner layer 5 is equal or lower than one third (1/3) of the total thickness of the main insulation 3.
  • the outer layer 6 includes high thermal conductivity inorganic particles 7 such as Boron Nitrite or corundum with grain size below 0.2 mm.
  • the electric field is very strong in a zone close to the conductive element 2 but decreases when departing from the conductive element 2, thus the first layer 5 has optimised electric features and the outer layer 6 has optimised thermal features.
  • the thickness of the first layer 5 being not greater than one third (1/3) of the total thickness of the main insulation allows optimised use of the insulating material. In fact after about one third (1/3) of the main insulation thickness, the electric field strength decreases such that focus can be switched on thermal features instead of electric features.
  • the gain in thermal transport properties can be increased by 20% due to a reduction in thickness of the entire insulation compared to the use of a high thermal conductivity tape alone and by more than 40% compared the use of a tape with optimized high field stability alone.
  • the inner layer 5 and the outer layer 6 are made of mica tapes having a different HTC particle content (HTC meaning high transport conductivity); these tapes are wrapped around the conductive element 2, are impregnated with a resin and the resin is then cured.
  • HTC high transport conductivity
  • boron nitride particles can be used as HTC particles.
  • the mica tape constituting the inner layer 5 has a low or no HTC particle content and the mica tape of the outer layer 6 has a larger HTC particle content than the inner layer 5.
  • stator bar In the following a second, preferred embodiment of the stator bar is described.
  • Optimized heat transfer must not be equalled with optimized thermal conductivity. Whilst thermal conductivity is a property of a material, an optimised heat transport from the conductive element 2 to the stator iron core through the insulation 4 requires an optimised heat transport also through the interface between the conductive element 2 and the insulation 4.
  • Such gaps can open due to the mismatch in thermal expansion between the conductive element 2 (made of copper) and insulation 4, since under thermal cycling a stress generates at their interface that leads to rupture of the bond, when it exceeds the adhesion force.
  • CTE coefficients of thermal expansions
  • the inner layer 5 is manufactured by wrapping a tape 10 made of a mica paper 11 bounded to supporting sheets 12 having equal thermal expansion at each of its sides; preferably the supporting sheets comprise glass and/or organic fibres such as thermoplastic or natural fibres.
  • the outer layer 6 comprises a mica free tape.
  • the outer layer 6 comprises a mica free, glass and/or organic fibre tape (i.e. no mica is contained in this tape).
  • the tape may comprise a woven glass or organic fibre fabric consisting of yarns or rovings or a non-crimp fabric.
  • the glass may consist of any kind of glass fibre and is not limited to E-glass fibres (i.e. to those fibres used as support sheets in mica tapes).
  • mixed fibres containing thermoplastic fibres, such as Aramide, polyamide, polyester, etc, in combination with glass fibres can also be used. Such mixed fibres may be used to reduce the dielectric permeability of the outer layer and/or adapt the coefficient of thermal expansion CTE.
  • This inner layer 5 prevents or hinders gaps from forming between the conductive element 2 and the insulation 4, since it has a coefficient of thermal expansion that matches the coefficient of thermal expansion of the copper (constituting the conductive element) within +/- 2 ppm/K; this lets the stress at the interface between the conductive element 2 and the insulation 4 be reduced.
  • the mica paper 11 distributes the stress on the two sheets 12 to which it is connected (instead of only one as in traditional mica tapes), further reducing the stress at the interface between the conductive element 2 and the insulation 4.
  • the outer layer 6 (made of glass and/or organic fibres) has a coefficient of heat transport very high, up to 1.0 W/mK or even larger; preferably it is about 1.5 W/mK.
  • An additional layer 15 may be placed between the conductive element 2 and the insulation 4 with a coefficient of thermal expansion (CTE) between the one of copper (constituting the conductive element 2) and insulation 4.
  • CTE coefficient of thermal expansion
  • This additional layer 15 helps to grade the mechanical stress.
  • the additional layer 15 is made of a weakly conductive material, at least at its inner side, to serve as inner corona protection.
  • the additional layer 15 exhibits a plastic or rubber-elastic properties (e.g. it could be a sticky silicon-elastomer or an epoxy-silicon-elastomer-blend); in this embodiment the additional layer 15 absorbs at least part of the shear forces elastically or plastically and, thus, reduces the stress at the interface between the conductive element 2 and the insulation 4.
  • the additional layer 15 may serve as inner corona protection, if it is made weakly conductive at least at its inner side.
  • the additional layer 15 has a weakly conductive inner side (i.e. the side towards the same conductive element 2) it has a surface conductivity between 10 Ohm cm/cm ⁇ R ⁇ 10'000 Ohm cm/cm.
  • stator bar may have an inner layer 5 according to the first embodiment above described and an outer layer 6 according to the second embodiment above described.
  • Manufacturing of the insulation is carried out by wrapping the tapes around the conductive element 2 and then impregnating them.
  • the use of the glass and/or organic fibre tape as the outer layer opens the way to novel production techniques.
  • mica tapes in combination with pre-impregnated glass tapes and to process them under vacuum and temperature.
  • the surplus resin serves to impregnate the mica tapes.
  • a plurality of tapes interleaved with resin films may be used (RFI-technique). This variant facilitates to improve the properties of the outer layer by introducing high thermal conductivity particles. If corundum or Boron Nitride fillers are used, the thermal conductivity will go up, if nano-sized oxides are used the dielectric strength may go up.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Insulation, Fastening Of Motor, Generator Windings (AREA)
EP10168358A 2010-07-02 2010-07-02 Barre de stator Withdrawn EP2403112A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP10168358A EP2403112A1 (fr) 2010-07-02 2010-07-02 Barre de stator

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP10168358A EP2403112A1 (fr) 2010-07-02 2010-07-02 Barre de stator

Publications (1)

Publication Number Publication Date
EP2403112A1 true EP2403112A1 (fr) 2012-01-04

Family

ID=42830373

Family Applications (1)

Application Number Title Priority Date Filing Date
EP10168358A Withdrawn EP2403112A1 (fr) 2010-07-02 2010-07-02 Barre de stator

Country Status (1)

Country Link
EP (1) EP2403112A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9819248B2 (en) 2012-12-31 2017-11-14 Teco-Westinghouse Motor Company Assemblies and methods for cooling electric machines

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19536209A1 (de) * 1995-09-28 1996-12-12 Siemens Ag Kombiband zur gleichzeitigen Herstellung einer Isolierung und eines Glimmschutzes und damit umwickelter elektrischer Leiter
DE19811370A1 (de) 1998-03-16 1999-09-23 Abb Research Ltd Variation der Dielektrizitätskonstanten in Isolierungen von Hochspannungswicklungen elektrischer Maschinen
US5973269A (en) * 1996-04-16 1999-10-26 General Electric Canada Inc. Multi-layer insulation for winding elements of dynamoelectric machines (D.E.M.s)
JP2001231206A (ja) * 2000-02-16 2001-08-24 Hitachi Ltd 高電圧回転電気機器の固定子
US6927342B1 (en) * 2000-06-23 2005-08-09 Von Roll Isola Winding Systems Gmbh Insulation for electrical conductors that produces no partial discharges
EP1933444A2 (fr) * 2006-12-15 2008-06-18 General Electric Company Diélectrique non linéaire utilisée comme isolation électrique
WO2008087093A1 (fr) * 2007-01-18 2008-07-24 Alstom Technology Ltd Tige conductrice pour le stator d'un générateur ainsi que son procédé de fabrication
US20080284262A1 (en) * 2004-06-15 2008-11-20 Siemens Power Generation, Inc. Stator coil with improved heat dissipation
EP2081278A2 (fr) * 2008-01-17 2009-07-22 ALSTOM Technology Ltd Barre conductrice pour machine électrique tournante

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19536209A1 (de) * 1995-09-28 1996-12-12 Siemens Ag Kombiband zur gleichzeitigen Herstellung einer Isolierung und eines Glimmschutzes und damit umwickelter elektrischer Leiter
US5973269A (en) * 1996-04-16 1999-10-26 General Electric Canada Inc. Multi-layer insulation for winding elements of dynamoelectric machines (D.E.M.s)
DE19811370A1 (de) 1998-03-16 1999-09-23 Abb Research Ltd Variation der Dielektrizitätskonstanten in Isolierungen von Hochspannungswicklungen elektrischer Maschinen
JP2001231206A (ja) * 2000-02-16 2001-08-24 Hitachi Ltd 高電圧回転電気機器の固定子
US6927342B1 (en) * 2000-06-23 2005-08-09 Von Roll Isola Winding Systems Gmbh Insulation for electrical conductors that produces no partial discharges
US20080284262A1 (en) * 2004-06-15 2008-11-20 Siemens Power Generation, Inc. Stator coil with improved heat dissipation
EP1933444A2 (fr) * 2006-12-15 2008-06-18 General Electric Company Diélectrique non linéaire utilisée comme isolation électrique
WO2008087093A1 (fr) * 2007-01-18 2008-07-24 Alstom Technology Ltd Tige conductrice pour le stator d'un générateur ainsi que son procédé de fabrication
EP2081278A2 (fr) * 2008-01-17 2009-07-22 ALSTOM Technology Ltd Barre conductrice pour machine électrique tournante

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9819248B2 (en) 2012-12-31 2017-11-14 Teco-Westinghouse Motor Company Assemblies and methods for cooling electric machines

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